Does anyone know what the effect is of a full moon at dark site? It would be equivalent to what color of sky on the light pollution maps for a moonless night?

The short answer is that it's equivalent to the white zone. The longer answer is that it's quite different, because the Moon's glow is distributed over the sky in a way fundamentally different from artificial skyglow. That results from the fact that artificial light wells up from the horizon, while moonlight shines down from above.

Very useful report Tony. LP from my London backyard obsy is severe to the point that late dusk just freezes and gets no darker. But I've a workaround via my cam in brief exposures which are stacked to go deeper ONCE the bright sky background is removed. The moon makes little difference to my imaging except for a few days around full moon when the skies are more polluted. :o